Why does this happen on hills ? Btw this is I 84 going to Connecticut

618559

{"replyTo":"","text":"It’s an automatic Allison transmission with Cummins Isb 6.7 straight truck. It turns out my truck had bad def, I removed the old def fluid and put new ones now it’s climbing hills easily ","replyToPid":0}

336899

{"replyTo":"","text":"no no no on 1800 - 2000 rpm. you can spin cam right off the motor. you are probably thinking of the old school motors. these days the electronic motors are made to run in very low rpm ranges. in old days you would have to much fuel going into the motor at low rpm.","replyToPid":0}

336899

{"replyTo":"

576904 发表于 2020-01-10 00:28:51 I'm going to agree to disagree with you on this subject.  I don't know the gears for the gentleman's truck which started this thread, however, I'm running 3:42, with a manual transmission.  I have found my truck runs cooler and uses less fuel when climbing in 5th gear at approximately 30 ish km/h (approx 20 m/h) at approximately 1350 to 1400 rpm's. she's not working hard and she'll pull like that all day long.  my truck is well tuned and looked after. Oil viscosity tests are all good, plus it's easier on tires, the rear ends, drive line etc etc.... \n\nas an experiment, I've powered up hills, which the DD15 at 505hp has lots of power, and I've found pulling hills as I've described has been better in performance for my truck. running up a hill with higher rpm's has showed higher oil temp, higher axle temps and an increase in fuel consumption. \n\nthanks for the alternate opinion! \n\ncheers!

","text":"you are absolutely correct.","replyToPid":301505}

336899

{"replyTo":"

688068 发表于 2019-12-31 02:30:15 1400 rpm?? assuming it a standard otr truck, it's most likely higher geared,  343....273...with that low of rpm pulling a grade, you'll cook your pistons! the exhaust temps will be much higher.  Keep it around 1800-2000 r's when climbing a grade.

","text":"no no no on 1800 - 2000 rpm. you can spin cam right off the motor. you are probably thinking of the old school motors. these days the electronic motors are made to run in very low rpm ranges. in old days you would have to much fuel going into the motor at low rpm and would ruin the motor. welcome to the 21st century 😏","replyToPid":293893}

336899

{"replyTo":"

618559 发表于 2020-01-16 17:14:13 It’s an automatic Allison transmission with Cummins Isb 6.7 straight truck. It turns out my truck had bad def, I removed the old def fluid and put new ones now it’s climbing hills easily

","text":"that explains no high RPMs since it's a straight truck. besides you have no control over that since it's an automatic. \nyeah you were probably derating.","replyToPid":306555}

686228

{"replyTo":"","text":"so am I the only one that got a bit of a stiffy when frog started talking gear ratio?","replyToPid":0}